Devices for the rapid qualitative and/or quantitative detection of analytes in a liquid sample often involve a sandwich type assay, frequently immunoassay, wherein certain reagents necessary for performance of the assay are located within the device. The device reagents are typically disposed within in the device in a dry form. During storage of the device prior to use, it is desirable to prevent adsorption and/or absorption of moisture onto the dry reagents, in particular for reagent that may be inactivated or desensitized by water molecules. Chemical drying agents, e.g., desiccants, for absorbing/adsorbing moisture are known in the art, and are typically included, for example, as a separate sachet in the package for the device or in a separate compartment of the device. There remains a need, however, to reduce or prevent moisture uptake by reagents and other components in a diagnostic assay device, where the desiccant is incorporated in such a way that it cannot contaminate the device reagents nor interfere with performance of the device. It is further desirable that such desiccant be incorporated in a manner that can improve manufacturing efficiencies, for example by decreasing manufacturing time and/or costs.